At the PhotoPlus Expo this past September I stopped by the Sony booth. Having received pre-show information, I wanted to try their pair of new cameras – the Alpha A33 and A55. While both look and function like DSLRs, a more appropriate term might be DVF – Digital ViewFinder – since neither uses a reflex mirror. Instead, they sport a fixed translucent “mirror” that sends a small portion of the incoming image to the viewfinder and the remainder to the “film” light sensor.

This technology isn’t new. In the early 1960’s Canon made a model called the Pellix using a similar scheme with a pellicle mirror. My uncle bought this camera back then, one of the first to have Through The Lens metering (TTL) and it served him well for many years.

Sony believes that their updated translucent mirror has life in the 21st century. There are several advantages to such an arrangement. First, a static mirror eliminates the reflex mechanism providing a space, weight and cost savings. Removing this mechanical assembly also allows for a higher frame rate. Next, the electronics measuring the auto exposure remain uninterrupted from frame to frame giving instant responses to varying changes in lighting. Similarly, the auto focus system stays 100% available – a very important consideration for high speed continuous shooting.

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